Recently, with respect to fabrication of thin film devices provided with thin film transistors (TFTs), thin film diodes (TFDs), etc., techniques have been examined in which a thin film device that is lightweight, excellent in shock resistance and is flexible is fabricated by transferring a thin film element, for example, to a flexible substrate that has flexibility from an original fabrication substrate, in which the thin film element is fabricated.
For example, the applicant has developed a method for transferring a thin film element fabricated on an original fabrication substrate to a flexible substrate that serves as a substrate to be transferred, and for which an application has been applied (Japanese Unexamined Patent Application 10-125931). In the method, a thin film element is fabricated on the original fabrication substrate with a peeling layer. Then, it is adhesively bonded on a substrate to be transferred and irradiated with light. As a result, a separation occurs to peel off the original fabrication substrate from the thin film element.
The applicant also has developed a transfer method in which a thin film element is transferred to a temporary transfer substrate (the first transfer body) as the first transfer and then transferred to a second transfer substrate (the second transfer body) as the second transfer. Patents have been applied for relating to this method (Japanese Unexamined Patents 11-26733 and 2001-189460).
With these transfer methods, flexible thin film devices can be fabricated by the following manners: a thin film element that requires high temperature processes and high processing accuracy in fabrications is fabricated on an original fabrication substrate that is excellent in heat resistance and shape stability, and is suitable for fabricating the thin film element; and then the thin film element is transferred on a substrate, for example, such as a resin substrate that is lightweight and is flexible.
However, the flexible thin film device fabricated by using conventional transfer techniques as mentioned above has a disadvantage in that handling is difficult due to an unstable shape while the flexible thin film device is lightweight and flexible. That is, the same method for handling conventional glasses or silicon wafers easily causes mistakes of dropping, etc., in holding or transferring a substrate due to the pliability of the substrates. Particularly, in a case where a thin film device is fabricated in large quantity that is divided into a comparatively small area of approximately from several square millimeters to several square centimeters, it is very difficult to handle each thin film device individually and to conduct inspection or mounting processes promptly.
In addition, transferring a layer to be transferred to a transfer body that is soft (like film) makes a peeling operation difficult. Even if a transfer body that is hard is used as a temporary transfer substrate (the first transfer body), a problem still arises in which the first transfer body is hardly detached from the second transfer body (to which a layer to be transferred is bonded if a substrate to be transferred (the second transfer body) to which the transfer is finally conducted) is composed of a material that has pliability or flexibility such as film, etc.
Also, even if the first transfer body is composed of a material that can be removed by etching etc., for example, a problem arises in which material selection is complicated.